Interest-computer.



PATENTED JULY 7 L. M. LANDING.'

INTEREST COMPUTER.

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iT/ves ees No. 733,054. PATENTED JULY 7. 1903. L. M. LANDING.

INTEREST GMPUTER.

APPLICATION HL D .1a 1902. No MODEL. E MAR 2 SHEETS-SHEET 2.

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structions and combinations hereinafter detransverse slots l0 10 and l1 1l, preferably arranged as shown, and also with the longitudinal slot 13.

In Fig. l of the drawings the parts represented by the shaded lines arc thc portions of UNITED STATES I Patented July '7, 1903.-

PATEN'T OFFICE.

INTEREST-COMPUTER.

SPECIFICATION forming part of Letters Patent No. 733,054, dated July 7, 1903.

Application flied March 18, 1902.'

To all whom, it may concern:

Beit known that I, LABS MULDRUP LAND- ING, of Glenwood, in the county of Pope, State of Minnesota, have invented certain Improvements in Interest-Computers, of which the following is a speciiication.

This invention relates to improvements in computers designed to simplify the figuring of all kinds of interest and time as applied to simple interest, bank-discount, annual intercst, partial payments, averaging` accounts, dac., as well as lessening the possibility of error in such computations.

The invention consists, generally, in an interest-computer provided with a slotted front plate having thereon suitable words and figures indicating the months of the year, the days of the month, and the amount obtained by the multiplication of any number from one to one hundred by any number representing an annual rate of interest, together with a movable slide, properly figured and so arrranged as by its movement to indicate the interest on one dollar for any number of years, months, or days.

The invention consists, further, in the conscribed, and particularly pointed out in the claims.

In the accompanying drawings, forming part of this specication, Figure l is a front elevation of an interest-computer embodying my invention. Fig. 2 is a longitudinal section of the same. Fig. 3 is a front elevation of the back plate.

In the drawings, 2 represents a suitable base or back plate, preferably formed of wood or other suitable material and having a smooth thin plate 3 preferably secured thereto. A suitable ledge 5 is preferably formed around the edge of the plate 3, and a plate 7 is secured over the ledge 5, thereby bringing the back of said plate a slight distance away from the plate A plate f) is arranged between the plates 7 and 3 andis free to slide longitudinally in the space between said plates. The plate 7 is provided with the Serial No. 98,757. (No model.)

the rear or back plate 9 which are to be seen through the slots l0, Il, and I3. The front plate '7 is divided into two divisons by the transverse line l5, and the slots hereinbefore described are allarranged above said line. The space at-the left hand of the slot 13 is divided into two columns byv suitable lines marked thereon, and the space at the righthand side of said slot is divided into nine parallel columns. The space below the line l5 is also preferably divided into nine vertical columns. The rst column at the right of the slot 13 has its spaces marked, preferably, from 2 to 46. At the top and bottom of these columns are the numerals I to 9, arranged consecutively, and each column at the rightof the iirst has a number represented by the multiplication of the con' responding ligure in said first right-hand column by the number of the column, as indicated by the iigure placed at the top of the column. The columns in the lower division, or below the line l5, are similarly marked at the top and bottom, and the iirst column contains in consecutive order the numerals 47 to 99, and the succeeding columns contain the result of multiplication of the figures in the iirst column by the figures at the top or bottom of the respective succeeding vertical column. The columns at the left of the vertical slot 13 are marked with the names of the months and with numerals indicating the order of said months, beginning with February and ruiming through to the end of the year and then being followed by the names of all of the months in the succeeding year. The other column contains the figures corresponding to the names of said months. The plate 9 contains also a series of vertical columns and a series of perforations l5', preferably arranged at about the center of the plate and, if preferred, between the iigures forming the numerals for the days of the months. Therst column to the left of the center contains the words indicating in order the names of the months and the numbers represented by the order in which said months occur in the calendar year. The other vertical columns contain an amount representing the interest on one dollar at the given rate per cent. for any number of days from one' to thirty, for any number of months from one to twelve, and for ICO any number of years from one to six. The lower part of the plate has at the left of the center two columns of iigures running in the rev-erse direction,one of them containing numbers representing the months oi theyear, represented by the numerals 1 to 12, and the other corresponding numerals, but beginning with 0 and running to 11.

The operation of the device is as follows: In computing time carefully note the following: Vhen the number representing the day of the month from which time is to be computed is less than the number representing the day of the month to which time is to be computed, use the inside iigures for months and days, as seen through the slots 11 11. lVhen the number representing the day of the month from which time is to be computed is greater than the number representing the day of the month to which time is to be computed, the outside figures, shown through the slots 11 11, are to be used. Computation is always made from the months on the sliding plate to the months on the front plate 7 The months on the front plate marked First year are always in the same year as the year computed from on the slide, whatever year that may be, and the months on the front plate marked Second year are in the year following. The crossing of the line marked New year changes the year. Vith the slide moved to its upper position take month of starting found on the slide and by inserting a pencil or pointer into the hole opposite said month move the slide downward until this month is opposite the name of the month of settlement or month to which time is to be computed, found on the front plate, and through the slots 11 may be seen the time in months between the two months taken. lf the slide is not moved far enough to carry the name of the month from which computation is to be made across the line marked New year, both months are in the same year; but if the name of the month from which computation is made passes the line marked New year the month to which computation is to be made is in the next year. The operator must remember this in computing succeeding years up to the required time, as this computation is made mentally. Likewise, with the slide at its upper position, iind the smaller of the days of the months between which computation is to be made and move the slide down until said number isopposite the other number representing the other day of the month to be used in computation, and through the slot 11, marked Days, can be seen, in time, the number of days between the two dates used. If the earlier date in actual time comes earlierin themonth than the later day in actual time, so that the computation is made froma number on the plate to a smaller number on the slide, the number of days required in the computation will be shown by the in side iigures. If, however, the earlier date in actual time is represented by the larger number, use the outside figures shown in the right-hand slot 11. The number of years will of course be computed mentally, and the operator will now have the time between the two dates represented by years, months, and days. To find the interest on one dollar for this time, iirst insert the pointer into one of the holes on the side below the word Years and move the pointer down until it strikes the end of the slot in the recess shown in Fig. 1 of the drawings. The interest on one dollar for a given number of years at six, seven, eight, or ten per cent. will be shown through one oi' the slots marked 10. In order to find the interest for the given number of months, insert the pointer into one of the holes below the word ""llonths on the slide and move the slide down until the pointer strikes the end o'l' the slot, and the interest on one dollar will then be shown through the left-hand slot 11 or the one that is marked Mo. Ina similar manner to iind the interest on any number of days from one to thirty insert the pointer in the proper hole in the slide below the word Days and move the slide downward until the pointer strikes the end of the slot. The interest for the number of days willnowbe shown through the slots 10. These three amounts added together will give the interest on one dollar for the req uii ed number of years, days, and months. To iind the interest on any number of dollars, multiply the interest on one dollar by the number of dollars. If it is required to iind the interest on tens, hundreds, or thousands of dollars, it is only necessary to move the decimal point the required distance to the right inthe amount representing the interest on one dollar. The other columns of figures on the front plate furnish a ready means for permitting this multiplication. illustration of the method oi' computing interest with this device. For instance, to find interest on sixty-nine dollars and fifty cents at ten per cent. from February 7, 1900, to Hay 30, 1900, we note iirst that the earlier day of the month is represented by the numeral 7 and the later day of the month by the numeral 30. Ve therefore use the inside column of figures, representing months and days, asshown through the slots 11. YV e first insert the pointer into the hole in the slide 9 that is opposite the word Feb. and we move the pointer down until the word Feb comes opposite the word May on the front plate of the device. The iigure 3 will now be shown at the linside or right hand of the left-hand slot 11 and will represent the time in months. Now move the slide back to its original position and insert the pointer in the hole marke( 7, near the top of the slide, and move the slide down until the 7 comes opposite the numeral 30 at the right of the slot. The number of d( ys will be shown through the slot 11 and at the left hand thereof and will be found to be 23. The time is therefore shown to be IOO This will readily be understood by an ITO IZO

three months and twenty-three days. Now insert the pointer in the hole marke( 3, below'the word marked Months on the slide, and move the pointer down until it strikes the bottom of the slot. The interest on one dollar at ten per eent. for three months will be shown at the left hand of the slot 10, or above the 10% on the plate 7. This will befoundtobe.025. Theninsertthepointer into the hole marke( 23 in the slide 9 and move the slide downward until the pointer strikes the end of the slot. The interest on one dollar for twenty-three days at ten per cent. will be shown at the same place and the amount now shown will be .00638. sum of these two amounts, or.025 plus .00638, equals .03138, which is the interest on one dollar for three months and twenty-three days at ten per cent. To lind the interest on sixtynine dollars for this time, multiply sixtyaiine by this number. To multiply sixty-nine by three, (the first figure at the left,) we look upon the lower part of the plate 7 and we iind opposite the number 00 and under the Column marked 3 the number 207 Proceeding in this manner we secure the result as follows:

This computer is iigured for thirty days to the month, or three hundred and sixty days per year. Bearing in mind that when the day of the month from which the Computation is to begin is represented by a larger number than the day of the month at which the computation is to end and that when the month from which the Computation is to begin is represented by a larger number than the month at which the computation is to end, the out- The side iigures in the slot 11 will be used in oomputation of time, and consequently any computation of interest may be quickly and readily made. IVhile I have shown the computer arranged to Compute interest at six, seven, eight, and ten per cent., it will be understood that it may readily be enlarged or added to, so as to make the computation for any other rate per cent.

The details of the construction may of eourse be varied in many particulars without departing from my invention.

I elaim as new and desire to secure by Letters Patent- 1. The combination, with the slotted front plate 7, of the sliding plate 9, provided with a series of numbered holes representing years, months and days, and with columns of figures representing the'interest on one dollar for the designated years, months or days, at different rates of interest, whereby upon insertion of a pointer in any one of the holes, and movement of the slide until the pointer strikes the end of the slot, the amount of interest upon one dollar for the corresponding number of years, months or days will be shown through the slotted front plate, substantially as described.

2. The combinatiomwith the slotted front plate 7, of the movable plate or slide 0, said slide being provided with the names of the months of the year, arranged in order, and with a series of numbers representingl said months, and said front plate being provided with two series of names, which represent the months of the year, arranged in the order of said months, whereby upon the movement of said slide to bring the name of any month thereon opposite the name of any month upon the plate, the number of intervening months will be shown through a slot in the front plate, substantially as described.

In testimony whereof I have hereunto set my hand this 11th day of March, 1002.

LARS MULDRUP LANDING.

In presence of- A. C. PAUL, q O. G. HANsoN. 

